feat(resources): reclaim banner controls and accurate reclaim math (#1318)

* feat(resources): reclaim banner controls and accurate reclaim math

Make the Resources Hub reclaim banner match what it advertises and give
operators control over when it appears.

- "Review & prune" now reclaims every category the banner lists (unused
  images, stopped containers, and dangling volumes) instead of images
  only, so the banner clears in one action. Pruning runs volumes first,
  while stopped containers still reference their named volumes, so a
  stopped stack's data is never cascaded into deletion.
- Add a "Show reclaimable-space banner" toggle under Settings, System,
  Docker hygiene (on by default, per node) and a dismiss control on the
  banner that snoozes it until the reclaimable total grows again.
- Fix the reclaimable-space math: count only containers a prune can
  actually remove (created, exited, dead) and size them by their writable
  layer, so a small, un-prunable remainder no longer keeps the banner up.

* fix(resources): show the reclaim banner when the settings fetch fails

A failed or empty /settings load left the banner's enabled flag at the
previously active node's value, so switching from a node with the banner
turned off to a node whose /settings errored kept the new node's banner
hidden. Set the flag unconditionally after the staleness guard so a
failed fetch falls back to the default-on state for the current node.

docs/features/resources.mdx

@@ -15,6 +15,10 @@ When there is reclaimable disk space (unused images, stopped containers, or dang
 
 The hero stays hidden when there is nothing to reclaim, keeping the view focused on the rest of your inventory.
 
+To set the banner aside without pruning, use the **×** in its top-right corner. It stays hidden on that browser until the reclaimable total grows past the amount it held when you dismissed it, so a small, stubborn remainder will not keep reappearing while a genuine new build-up still surfaces.
+
+To keep the banner off for a node entirely, open **Settings → System → Docker hygiene** and switch off **Show reclaimable-space banner**. It is on by default and applies per node.
+
 <Note>
   The banner and the **Review & prune** action are admin-only. Read-only roles still see the rest of the page but cannot trigger destructive operations.
 </Note>
@@ -219,4 +223,7 @@ When no unmanaged containers are detected, the tab shows a success state with th
   <Accordion title="I expected to see the Sencho container in the Unmanaged tab and it is not there">
     The Unmanaged tab filters the running Sencho container out by design so it cannot be selected and purged. Other containers started outside Sencho (with `docker run` or by a Compose project outside `COMPOSE_DIR`) still appear normally. To inspect the Sencho container itself, use **Host Console** or `docker ps` on the host.
   </Accordion>
+  <Accordion title="The reclaim banner will not go away, or shows a small amount that will not prune">
+    The banner mirrors what Docker reports as reclaimable on the node, and it counts only the resources a standard prune can actually remove. After a prune, some storage drivers still report a few megabytes as reclaimable that the prune does not free. To stop the banner drawing attention to a stubborn remainder, dismiss it with the **×** in its top-right corner; it stays hidden until the reclaimable total grows past that point. To turn it off for the node entirely, switch off **Show reclaimable-space banner** in **Settings → System → Docker hygiene**.
+  </Accordion>
 </AccordionGroup>